In short - MP3s need to be tagged with:
ID3V2.3
For Linux users, download EasyTag, and go to "Preferences" and set the tags to ID3V2.3. Then just click save and it'll reformat all your tags to the correct version!
To install EasyTag for Ubuntu or Debian users, in a command line, simply type:
Code: Select all
sudo apt-get install easytag
Hope this helps someone - I spent weeks trying to figure out why only some of my MP3s work!